Stellar MPP Payments Skill

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Built by ASG Card as a community-facing companion to our earlier Stellar x402 work.

This repo is for builders who want to understand or ship Machine Payments Protocol (MPP) flows on Stellar without starting from a blank page.

What This Repo Gives You

One install. Your AI agent learns how to:

• build payment-gated APIs with WWW-Authenticate: Payment
• build agent clients that answer 402 Payment Required automatically
• use Soroban SAC transfers for one-time MPP charges
• reason about one-way channels for higher-frequency payments
• adapt an existing Stripe MPP mental model to Stellar MPP

In practical terms, this repo gives the user:

• a reusable AI skill they can install into Codex, Claude Code, Cursor, Windsurf, or Gemini
• a seller example they can run locally
• a buyer example they can run locally
• focused references for charge mode, channel mode, and package choices
• guardrails for replay protection, side-effect safety, and settlement design

Why A User Would Need This

MPP on Stellar is still early. Most builders have to piece the flow together from protocol docs, SDK internals, and scattered examples.

This repo compresses that work into something runnable.

Use it if you are:

• building a paid API and want a clean first implementation
• building an agent that should pay for resources automatically
• evaluating whether charge or channel mode is the right fit
• coming from Stripe MPP and need a credible path onto Stellar
• teaching an LLM-powered coding agent how to scaffold these flows correctly

What Is In This Repo

stellar-mpp-payments-skill/
├── .cursorrules                         # Cursor / Windsurf hook
├── install.sh                          # One-command installer
├── examples/
│   ├── stellar-mpp-server/             # Seller example: payment-gated API
│   └── stellar-mpp-client/             # Buyer example: automatic 402 payment client
└── stellar-mpp-payments/
    ├── SKILL.md                        # Main skill and decision tree
    └── references/
        ├── charge.md                   # One payment per request
        ├── channel.md                  # Off-chain commitment flow
        ├── packages.md                 # Package matrix and install guidance
        └── stripe-interop.md           # Stripe MPP -> Stellar MPP migration notes

What A User Can Do In 10 Minutes

1. Install the skill.
2. Run the server example.
3. Run the client example.
4. Watch a real 402 -> Payment -> verified response flow.
5. Decide whether to keep building with charge mode or move to channel mode.

Quick Install

curl -sSL https://raw.githubusercontent.com/ASGCompute/stellar-mpp-payments-skill/main/install.sh | bash

The installer copies the stellar-mpp-payments skill into Claude Code, Codex, Cursor/Windsurf, or Gemini locations.

Manual Install

Claude Code

git clone https://github.com/ASGCompute/stellar-mpp-payments-skill.git
mkdir -p ~/.claude/skills
cp -r stellar-mpp-payments-skill/stellar-mpp-payments ~/.claude/skills/

Codex

git clone https://github.com/ASGCompute/stellar-mpp-payments-skill.git
mkdir -p ~/.codex/skills
cp -r stellar-mpp-payments-skill/stellar-mpp-payments ~/.codex/skills/

Cursor / Windsurf

git clone https://github.com/ASGCompute/stellar-mpp-payments-skill.git
cp stellar-mpp-payments-skill/.cursorrules ./
cp -r stellar-mpp-payments-skill/stellar-mpp-payments ./

Gemini

git clone https://github.com/ASGCompute/stellar-mpp-payments-skill.git
mkdir -p ~/.gemini/skills
cp -r stellar-mpp-payments-skill/stellar-mpp-payments ~/.gemini/skills/

Live Examples

Two ready-to-run projects live in examples/.

Seller: Stellar MPP Server

A small Express API that charges 0.01 USDC per request on Stellar testnet.

cd examples/stellar-mpp-server
npm install
npm run dev

Buyer: Stellar MPP Client

A Node client that catches a 402 challenge, signs the Stellar payment, and retries automatically.

cd examples/stellar-mpp-client
npm install
npm start

How The Repo Thinks

The skill teaches a simple decision tree:

User asks about MPP / paid APIs / machine payments on Stellar
│
├─ Are you the SELLER or BUYER?
│  ├─ Seller -> protect an API or action behind payment
│  └─ Buyer  -> automatically pay for a resource
│
├─ Which PAYMENT MODE?
│  ├─ Charge  -> one on-chain SAC transfer per request
│  └─ Channel -> many off-chain commitments, occasional close
│
├─ Which NETWORK?
│  ├─ Testnet -> demos, pilots, first integrations
│  └─ Public  -> production settlement
│
└─ Are you MIGRATING FROM STRIPE MPP?
   ├─ No  -> use normal Stellar MPP setup
   └─ Yes -> preserve protocol shape, swap settlement rail

Why This Is Useful Beyond Docs

It is a small packaging layer that helps both humans and AI coding agents do the right thing faster:

• the skill tells the model how to reason about the task
• the references keep protocol and implementation choices organized
• the examples give runnable code, not just theory
• the installer makes adoption low-friction

Relation To x402-payments-skill

This repo is the MPP companion to the earlier Stellar x402 community asset.

• x402-payments-skill teaches x402 on Stellar
• stellar-mpp-payments-skill teaches MPP on Stellar

The protocol ergonomics overlap, but the implementation model differs:

• x402 centers on x402 challenge/accept flows and facilitator-style settlement
• MPP centers on the Payment auth scheme and method-specific credentials
• this repo adds explicit guidance for charge vs channel and Stripe-to-Stellar migration

Why ASG Card Is Sharing This

After completing a pilot that combined Stellar settlement, MPP flows, and Stripe-style machine payment concepts, we packaged the useful parts into a public community asset.

This repo is meant to save other teams time:

• start with a working skill instead of blank docs
• see a clean seller/client split
• understand when to choose charge vs channel mode
• avoid obvious replay and side-effect mistakes

License

Apache-2.0. It stays permissive, but is a better fit for a public developer integration asset because it includes an explicit patent grant.

Project Links

Repo · x402 Companion · ASG Card · stellar-mpp-sdk